Made QImage::fill(uint pixel) for RGB888 accept QRgb values.

Made QImage::fill(uint pixel) for RGB888 accept QRgb values.

Previously QImage::fill() for Format_RGB888 expected a BGR value
instead of the RGB order defined by QRgb, making it counter intuitive to
use related to the 32-bit formats.

Fixed the QPixelLayout data for RGB888 and changed the byte order of
quint24 based on what the optimized image conversion routines expect.

Change-Id: I72926debbc6f5b5cb10b8aa0b2a2a916a04db946
Reviewed-by: Kim M. Kalland <kim.kalland@nokia.com>